This invention generally relates to renewable energy sources, and more particularly, to systems and methods for controlling power in renewable energy sources.
Solar, wind and hydro power generation systems are generally categorized as renewable variable power generation systems because the energy is harvested from naturally occurring and plentiful sources of energy. However, the amount of power produced by such systems may be unstable. The power generated by a solar farm for example, may vary as a function of cloud coverage and the position of the sun in the sky. Such a solar farm may have a plurality of energy harvesting panels with associated photovoltaic cells and inverters that may require power monitoring and control for coordinating and providing power to an electrical grid. For example, a utility may monitor the grid power demand and may need to communicate with the solar farm to determine if the solar farm has the capacity to meet some or all of the power demand.
It is common to connect many small solar inverters to the electrical grid, making the collection of inverters appear as one power plant. Electrical power grids generally require both a source of active power and a source of reactive power. Active power (Watts) is generally provided to the electrical grid based upon the capacity of each power generation system inverter. Reactive power (VARs) is generally proportioned equally among the inverters based upon the number of inverters in the power generation system. Such proportioned reactive power generation disadvantageously results in a loss of expensive active power from highly productive inverters due to equal sharing.
In view of the foregoing, there is a need for a power inverter system and method of operation that distributes reactive power support from among multiple power inverters, favoring those inverters that have remaining capacity, rather than dividing the total VAR support equally among all the inverters, especially those inverters operating at the maximum rated output power.